Synthesis and Cyclization of 1-(2-Hydroxyphenyl)-2-propen-1-one Epoxides: 3-Hydroxychromanones and -flavanones <i>versus</i> 2-(1-Hydroxyalkyl)-3-coumaranones
作者:Tamás Patonay、Albert Lévai、Csaba Nemes、Tibor Timár、Gábor Tóth、Waldemar Adam
DOI:10.1021/jo960163z
日期:1996.1.1
Competitive alpha and beta cyclization of 2'-hydroxychalcone epoxides affords 2-(alpha-hydroxybenzyl)-3-coumaranone and/or 3-hydroxyflavanones, which depends on the conditions employed. Epoxidation of 2'-hydroxychalcones by dimethyldioxirane followed by either base- or acid-catalyzed ring closure provides a novel, general, and efficient method for the synthesis of trans-3-hydroxyflavanones, which includes also the naturally occurring derivatives. Extension of this two-step procedure to 1-(2-hydroxyphenyl)-2-alken-1-ones was also accomplished. A strong preference for alpha cyclization was observed in the case of beta-unsubstituted or -monoalkylated alpha,beta-enones, while both 2,2-dimethyl-3-hydroxychromanones and 2-(1-hydroxy-1-methylethyl)-3-coumaranones were obtained from the beta,beta-dimethylated substrates.
An Efficient Synthesis of Highly Functionalized [5,6] Aromatic Spiroketals by Hetero-Diels−Alder Reaction
作者:Guanglian Zhou、Jianrong Zhu、Zhixiang Xie、Ying Li
DOI:10.1021/ol7029068
日期:2008.3.1
A hetero-Diels-Alderreaction of vinyl sulfoxides with o-quinone methides precursor constructs highlyfunctionalized [5,6] aromatic spiroketal skeletons in moderate to good yields with high regioselectivity. The two functional groups (ketone and olefin) can be further subjected to many synthetic transformations.